mobile | classic
Dataweek Electronics & Communications Technology Magazine





Follow us on:
Follow us on Facebook Share via Twitter Share via LinkedIn


Search...

Electronics Buyers' Guide

Electronics Manufacturing & Production Handbook 2019


 

Single-chip power manager sequences, monitors and supervises up to seven channels
5 November 2003, Power Electronics / Power Management

The design of systems with multiple supply voltages is commonplace today. In such systems as Internet routers, digital subscriber-line access multiplexers (DSLAMs), base stations, and servers, the sequencing and supervision of their multiple supplies has grown in importance.

This article shows how the ADM1060 supervisor/sequencer from Analog Devices greatly simplifies this task by providing multiple supply supervisors, sequencing logic, and multiple-output drivers, in a single 28-lead TSSOP device. Also, the configuration of these multiple functions is easily programmed using the company's intuitive graphical user interface (GUI).

User demands is making the design task increasingly difficult. Customers want more channels at higher data rates for less money. They also require a much higher level of reliability: An uptime of 99,999%, commonly known as 'five-9's reliability' (analogous to two minutes of downtime per year), is now a basic requirement.

Additional bandwidth, expressed in both channel count and speed, has resulted in a proliferation of many new-generation devices. The cores of these devices run at much lower voltages than the traditional 3,3 V or 5 V (for example, 1,2, 1,5, 1,8, and 2,5 V are common core-supply levels). Yet I/O protocols dictate that 3,3 and 5 V supplies still be provided. In fact, some designs may require a 12 V supply; others need termination voltages as low as 0,75 V; and there are even cases where negative supplies are required for op-amp rails.

It is not uncommon for many, if not all, of these supplies to be required on a single board - easily for six, seven, or more supplies. The sequence in which the supplies turn on can be critical to the reliable operation of the system. A good rule of thumb might be to start with the highest supply first and work downwards; but this is not always the case. For instance, some DSP manufacturers recommend that the core of their device be powered up before the I/O, while others recommend the opposite. Given the PCB complexities now, the truth is that it may be difficult to determine what the optimal power-up sequence is without first designing, building, and testing. But this 'trial-and-error' is costly.

The current discrete approach to supply sequencing, using reset generators, FET drivers, and RC time constants (Figure 1 shows a typical implementation) - while adequate for a system requiring two or three supplies, it becomes very cumbersome when the number rises to six or seven. Another problem is that accurate reset generators have fixed threshold voltages. If - as can be the case with ASICs - a supply voltage must be tweaked to a nonstandard value for maximum performance. Also, such designs require the power designer's best guess (albeit an educated one) as to the sequence required. If the wrong guess, it is difficult to rectify without a board spin. Further, as the PCB population density increases, real estate becomes an issue and a multicomponent discrete solution becomes unattractive. Finally, it is not easy to design the power-down sequence, using the same simple reset generators with fixed timeouts and open-drain outputs.

Figure 1. Discrete implementation for sequencing seven supplies
Figure 1. Discrete implementation for sequencing seven supplies

The solution described here is a single IC, which provides a total voltage-management solution and encompasses all of the functionality of the discrete design shown in Figure 1. The device also goes further, however, in providing the flexibility to change its configuration easily as required. If the alteration of a reset threshold, the power-up sequence, the power-down sequence, and the watchdog timeout on a processor clock can be altered without laying out the hardware again, the power designer's task is made infinitely easier. Naturally, a single IC (minimal external components) also addresses the key issue of board real estate. Also, the design is quicker and if necessary, it can be altered later without a change in hardware.

The Analog Devices ADM1060 multisupply supervisory circuit is such a device. A total voltage-management solution in a single small 28-lead package, it requires as few as two external parts (decoupling capacitors), making it ideal for applications where board space is at a premium.

The ADM1060 can supervise up to seven supplies. All of the supervisors on the chip use window comparators, so that both overvoltage and undervoltage supply faults can be detected on each of the supply fault input pins. One of the supply fault detectors can supervise a supply up to 14,4 V (analogous to a 12 V supply being overranged by +20%). Four of the supervisors can detect faults from 0,6 to 6 V (a 5 V supply being overranged by +20%). The other two supervisors can be used to monitor negative supplies down to -6 V. If supervision of a negative supply is not required, these two pins can be used to monitor supplies up to +6 V. Any threshold voltage within the above ranges can be programmed with 8-bit resolution. Thus, if an ASIC runs optimally with a nonstandard voltage ie, not 1,2, 1,5, 1,8 V, etc, the ADM1060 can be programmed around the modified supply voltage with an accurate fault-detection window. The hysteresis of these comparators is programmable digitally, allowing the user to control the level of noise immunity required.

The ADM1060 does not need a dedicated power pin. The device uses an arbitration scheme to power itself from any one of five of the supply-fault input pins. The highest is used, and if this should fail, the ADM1060 seamlessly switches over to the next highest supply to power itself. Thus, even in a failing system, the device continues to be powered, maintaining supervision for as long as possible.

The ADM1060 also provides four general-purpose inputs (GPIs). These are logic inputs (TTL- or CMOS-compatible) that enable the user to apply control signals, such as POWER_OK, RESET, or MANUAL RESET, and use these to control the sequence in which the supplies turn on. Note that these inputs can also be used to take signals from external supervisory chips, if more than seven supplies need to be supervised and included in the sequencing. A watchdog timer is also included that ensures that a processor clock continues to toggle.

The logical core of the device is the programmable logic-block array (PLBA), combined with the programmable delay block (PDB). These blocks enable the ADM1060 to sequence the turn-on of the supplies' programmable time delays in the chosen order. A set of different time delays can be programmed for a power-down sequence. For instance, a supply may be required to power up 100 ms after the previous supply - but to turn off instantly if a fault occurs.

The ADM1060 makes available nine output drivers. These programmable driver outputs (PDOs) can be used as logic-control signals, such as chip-enable, LDO- (DC/DC brick-) output enable, or simply as status signals. The output pins all have an open-drain configuration, allowing the user to connect an external resistor to pull the pin up to the desired voltage. However, it is likely that the pull-up voltage is one that is being supervised at one of the inputs of the device and is available on-chip. Therefore, the ADM1060 features a bank of internal pull-up resistors, which can be connected to the pull-up voltage without external components. This is of course significant where minimal board space is available. Four of the output drivers can also provide a high-voltage gate drive to turn on an NMOS FET, which may be placed in a supply path. In this option, a 12 V charge-pump voltage is provided at the output pin.

Communication with the ADM1060 is via an industry-standard 2-wire interface (SMBus). The user can set up the features described using the intuitive GUI provided by Analog Devices. This programming can be done offline, using the evaluation kit, or in-system, using a 3-pin header cable. Once satisfied with the configuration, the user can store this in nonvolatile memory, so that each time the device is subsequently powered up, the same configuration is downloaded and set up in the device.

Providing the same seven supplies outlined in the discrete design of Figure 1, a sequence could be implemented using a single ADM1060 as shown in Figure 2.

Figure 2. Sequencing the same seven supplies using a single ADM1060
Figure 2. Sequencing the same seven supplies using a single ADM1060

Another very powerful feature of the ADM1060, not easily replicated in a discrete design, is the ability to configure a controlled power-down sequence. Again, using the software provided, a sequence like that shown in Figure 3 can be configured.

Figure 3. Controlled power on/off sequence using the ADM1060
Figure 3. Controlled power on/off sequence using the ADM1060

Conclusion

The requirement for multiple voltages on a single PCB has resulted in a difficult supply sequencing problem for power designers. With six, seven, or more voltages required, discrete solutions are unwieldy and impractical. The ADM1060 from Analog Devices provides a powerful and flexible solution, making the configuration of supply thresholds, logic inputs, and supply sequencing a straightforward software design-rather than a costly and error-prone hardware design.

For more information contact Analog Data Products, a division of Avnet Kopp, 011 809 6100.


Credit(s)
Supplied By: Avnet South Africa
Tel: +27 11 319 8600
Fax: +27 11 319 8650
Email: sales@avnet.co.za
www: www.avnet.co.za
  Share on Facebook Share via Twitter Share via LinkedIn    

Further reading:

  • Battery design trends for IoT
    23 October 2019, Avnet South Africa, Power Electronics / Power Management
    Ultimately, the choice of battery for any application in the Internet of Things will depend on the power profile of the application, in combination with any environmental factors such as temperature.
  • Points to consider when running power supplies from portable generators
    23 October 2019, Accutronics, Power Electronics / Power Management
    Manufacturers of end systems should specify what class of generator their products should be used with, and should question what class was used if they do see equipment failures.
  • Developing opportunities around ‘hybrid’ renewable energy power plants
    23 October 2019, Forbatt SA, Power Electronics / Power Management
    If we let our imaginations run wild in the local context – and imagine the possibilities that come from having the cheapest energy in the world – the creative minds amongst us could have a field day.
  • High-voltage power supplies
    23 October 2019, Vepac Electronics, Power Electronics / Power Management
    The XP Emco range of high-voltage power supplies meets a wide range of high-performance demands. It includes a broad range of DC-DC converter modules with output voltages from 100 V to 10 kV in both proportional ...
  • Four approaches to implement a wearable sensor hub
    23 October 2019, Avnet South Africa, DSP, Micros & Memory
    As more sensors are added to nearly every electronic device including smartphones, tablets and wearables, more power is needed to run sensor data and turn it into useful information. Data retrieved from ...
  • 5 Watt AC-DC converter
    23 October 2019, Avnet South Africa, Power Electronics / Power Management
    Aimtec’s new AMEL5-277NZ is an AC-DC converter which has been designed to offer greater economies of scale due to greater production automation, leading to improved reliability and performance. The product ...
  • USB Type-C power controllers
    23 October 2019, Avnet South Africa, Power Electronics / Power Management
    Microchip announced two new solutions that simplify USB Type-C PD (Powered Device) designs to remove the traditional complexity and high costs associated with implementing USB Type-C in a range of applications.  ...
  • 0,6 A and 1 A point-of-load converters
    23 October 2019, Conical Technologies, Power Electronics / Power Management
    Traco Power announced a new addition to its TSR-WI range: the TSR-WI line is a set of non-isolated point-of-load (POL) converter series with an ultra-wide 8:1 input voltage range, which come in standard ...
  • High-precision automotive GNSS module
    23 October 2019, Avnet South Africa, Telecoms, Datacoms, Wireless, IoT
    Quectel Wireless Solutions announced the release of its LG69T module, an automotive-grade, dual-band, high-precision GNSS (global navigation satellite system) module that integrates dead reckoning (DR) ...
  • 19-inch compatible power supply units
    23 October 2019, Actum Electronics, Power Electronics / Power Management
    nVent Schroff offers pluggable, switch-mode power supplies and a variety of open-frame power supplies for open standards. The linear regulator range caters for extremely sensitive electronics applications ...
  • Step-down power modules
    23 October 2019, Power Electronics / Power Management
    The MagI3C-VDMM (Variable Step Down Micro Module) power module family from Würth Elektronik is being supplemented by more powerful 1 A and 1,2 A versions. The input voltage range (from 2,5 to 5,5 V) covers ...
  • High-power connectors
    23 October 2019, Avnet South Africa, Interconnection
    TE Connectivity introduced Multi-Beam Plus connectors, the latest evolution of its power connector line. The new connectors share the same low-profile dimensions and enable the same through-system airflow ...

 
 
         
Contact:
Technews Publishing (Pty) Ltd
1st Floor, Stabilitas House
265 Kent Ave, Randburg, 2194
South Africa
Publications by Technews
Dataweek Electronics & Communications Technology
Electronics Buyers’ Guide (EBG)

Hi-Tech Security Solutions
Hi-Tech Security Business Directory

Motion Control in Southern Africa
Motion Control Buyers’ Guide (MCBG)

South African Instrumentation & Control
South African Instrumentation & Control Buyers’ Guide (IBG)
Other
Terms & conditions of use, including privacy policy
PAIA Manual





 

         
    Classic | Mobile

Copyright © Technews Publishing (Pty) Ltd. All rights reserved.